1. Field of the Invention
The present invention relates to an image processing device for quickly extracting distance information from stereo images. The present invention realizes a distance extracting process with a simple circuit configuration at high speed, thereby providing an inexpensive initial visual information processing device. The art of the present invention is expected to be used for industrial products such as robot visions and in-vehicle safety monitor devices.
2. Description of the Background Art
A human's initial visual information process involves a function of extracting distance information obtained by two-eye stereo viewing in addition to a function of photo-sensing with high adaptability. In other words, a human's sense of sight has a function of processing image information to estimate three-dimensional information including the extent of the space from two two-dimensional patterns reflected on the retinas of both eyes. Above all, a function of instantly acquiring the distance to the target in the field of vision is one of the considerably important abilities for a human to act safely. The high-speed estimation of the distance to the target by the stereo viewing is also a considerably important image information processing technique to realize industrial products such as robot visions and in-vehicle safety monitor devices, and their commercialization has been strongly desired.
Distance (depth) estimation by stereo images is generally achieved by a correlation process for specifying the same target between two images, and a distance calculation process for calculating the distances from the two different view points on the basis of parallax information obtained from these view points.
Conventional stereo image processing devices has required a large number of time for a correlation process. This is because the amount of calculation necessary for the correlation process is huge and also because the device has a limited calculation capability. The amount of calculation necessary for the conventional stereo image correlation process is generally in proportion to the product of the third power of the number of pixels in the direction having a parallax and the number of pixels in the direction having no parallax. For example, in the case of image data consisting of about 100,000 pixels (352×288 pixels), the correlation process requires over 100 billion number of calculations. This involves the problem that even a processor with 100 GOPS (Giga Operations Per Second) could offer a process speed which does not satisfy 8 screens per second. The process speed of this level is insufficient for cars and other comparatively fast-moving devices to be put in the actual use. Therefore, it is an object of the present invention to estimate distance information from stereo images at higher speed as compared with conventional devices.